[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Triassic archosaur bipedality and cursoriality
- To: email@example.com
- Subject: Re: Triassic archosaur bipedality and cursoriality
- From: Tim Williams <firstname.lastname@example.org>
- Date: Mon, 2 Jul 2012 13:44:20 +1000
- Authentication-results: msg-ip2.usc.edu; dkim=neutral (message not signed) header.i=none
- In-reply-to: <4FF0F5F6.email@example.com>
- References: <CAMR9O1+UN16A2fwp_qquq-fWitenfWxvna7DxeWxNv7vC6nGfirstname.lastname@example.org> <CA+nnY_EQeWcvVWH6j4wDqfD7OOA-ksKv6w+prAzA4mJCjJCSpA@mail.gmail.com>
- Reply-to: email@example.com
- Sender: owner-DINOSAUR@usc.edu
Dan Chure <firstname.lastname@example.org> wrote:
> Fair enough, what you wrote was "don't appear to have been terribly useful"
> so my restating of that was inaccurate.
No Dan, your quote was accurate. :-) To clarify what I meant a, I
opined that in "many non-avian theropods the forelimbs don't appear to
have been terribly useful". Given that many theropods had forelimbs
that were short and/or had limited anterior reach and/or were clothed
in large feathers, this limited the ability of the forelimbs to seize
prey. "Forelimb-first" predation appears to have been quite rare
among theropods, although possible for certain long-armed
deinonychosaurs (where the feet also played a major role).
> Nevertheless, I suspect they were
> still of more use than that. As for carnotaurines, Carnotaurus has, as I
> recall, a rather large ungual on the manus, which to me looks like it might
> well have had some function.
This is the conical element tentatively identified by Ruiz et al.
(2011) as the ungual of phalanx of manual digit III of _Carnotaurus_.
Even if _Carnotaurus_ had an ungual phalanx (or more than one), I
wouldn't read too much into this in terms of function. Kiwis
(_Apteryx_) can also retain a manual phalanx, although apparently the
presence of this particular phalanx is variable between specimens.
> Has anyone looked at how forelimbs become
> reduced and lost in vertebrates, i.e. are there patterns of reductions (such
> as reduction and loss of unguals before reduction and loss of rest of
> digit, etc.) that might be of predictive value when looking at things such
> as the odd forelimbs of carnotaurines or alvarezsaurids? If we can discount
> that the limbs are being reduced, rather than dramatically specialized,
> that would be a good starting point for discussions and investigation.
The fact that wing-claws are present in some ratites, but not all, and
that this phenotype seems to be variable in kiwis, suggests that
loss/retention of unguals is unconnected with forelimb reduction or
loss of function.
Similarly, _Carnotaurus_ may retain at least one ungual (depending
upon interpretation), but the articulated manus of the closely related
_Aucasaurus_ preserves no unguals.